#3852 Initialize Optionals with empty instead of null

processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java

@@ -17,6 +17,10 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -367,6 +371,15 @@ public class Type extends ModelElement implements Comparable<Type> {
         return componentType != null;
     }
 
+    private boolean isType(Class<?> type) {
+        return type.getName().equals( getFullyQualifiedName() );
+    }
+
+    private boolean isOptionalType() {
+        return isType( Optional.class ) || isType( OptionalInt.class ) || isType( OptionalDouble.class ) ||
+            isType( OptionalLong.class );
+    }
+
     public boolean isTypeVar() {
         return (typeMirror.getKind() == TypeKind.TYPEVAR);
     }
@@ -1166,6 +1179,10 @@ public class Type extends ModelElement implements Comparable<Type> {
      *         FTL.
      */
     public String getNull() {
+        if ( isOptionalType() ) {
+            return createReferenceName() + ".empty()";
+        }
+
         if ( !isPrimitive() || isArrayType() ) {
             return "null";
         }

processor/src/test/java/org/mapstruct/ap/test/optional/nullvalue/OptionalDefaultMapper.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.optional.nullvalue;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Dennis Melzer
+ */
+@Mapper
+public interface OptionalDefaultMapper {
+
+    OptionalDefaultMapper INSTANCE = Mappers.getMapper( OptionalDefaultMapper.class );
+
+    Target map(Source source);
+}

processor/src/test/java/org/mapstruct/ap/test/optional/nullvalue/OptionalDefaultMapperTest.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.optional.nullvalue;
+
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Dennis Melzer
+ */
+@WithClasses({
+    OptionalDefaultMapper.class,
+    Source.class,
+    Target.class
+})
+@IssueKey("3852")
+public class OptionalDefaultMapperTest {
+
+    @ProcessorTest
+    public void shouldOptionalNotNull() {
+        Source source = new Source( null, null, null, null, null, null, null );
+        Target target = OptionalDefaultMapper.INSTANCE.map( source );
+
+        assertThat( target.getSomeString() ).isEmpty();
+        assertThat( target.getSomeInteger() ).isEmpty();
+        assertThat( target.getSomeDouble() ).isEmpty();
+        assertThat( target.getSomeBoolean() ).isEmpty();
+        assertThat( target.getSomeIntValue() ).isEmpty();
+        assertThat( target.getSomeDoubleValue() ).isEmpty();
+        assertThat( target.getSomeLongValue() ).isEmpty();
+    }
+
+    @ProcessorTest
+    public void shouldMapOptional() {
+        Source source = new Source( "someString", 10, 11D, Boolean.TRUE, 10, 100D, 200L );
+        Target target = OptionalDefaultMapper.INSTANCE.map( source );
+
+        assertThat( target.getSomeString() ).contains( "someString" );
+        assertThat( target.getSomeInteger() ).contains( 10 );
+        assertThat( target.getSomeDouble() ).contains( 11D );
+        assertThat( target.getSomeBoolean() ).contains( Boolean.TRUE );
+        assertThat( target.getSomeIntValue() ).hasValue( 10 );
+        assertThat( target.getSomeDoubleValue() ).hasValue( 100 );
+        assertThat( target.getSomeLongValue() ).hasValue( 200 );
+    }
+
+}

processor/src/test/java/org/mapstruct/ap/test/optional/nullvalue/SimpleConstructorMapper.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.optional.nullvalue;
+
+import org.mapstruct.InjectionStrategy;
+import org.mapstruct.Mapper;
+import org.mapstruct.NullValueMappingStrategy;
+import org.mapstruct.ReportingPolicy;
+import org.mapstruct.ap.test.nestedproperties.simple._target.TargetObject;
+import org.mapstruct.ap.test.nestedproperties.simple.source.SourceRoot;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Dennis Melzer
+ */
+@Mapper(
+    nullValueMappingStrategy = NullValueMappingStrategy.RETURN_DEFAULT,
+    injectionStrategy = InjectionStrategy.CONSTRUCTOR, unmappedTargetPolicy = ReportingPolicy.IGNORE
+)
+public interface SimpleConstructorMapper {
+
+    SimpleConstructorMapper MAPPER = Mappers.getMapper( SimpleConstructorMapper.class );
+
+    TargetObject toTargetObject(SourceRoot sourceRoot);
+
+}

processor/src/test/java/org/mapstruct/ap/test/optional/nullvalue/Source.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.optional.nullvalue;
+
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
+
+public class Source {
+
+    private final String someString;
+    private final Integer someInteger;
+    private final Double someDouble;
+    private final Boolean someBoolean;
+    private final Integer someIntValue;
+    private final Double someDoubleValue;
+    private final Long someLongValue;
+
+    public Source(String someString, Integer someInteger, Double someDouble, Boolean someBoolean, Integer someIntValue,
+                  Double someDoubleValue, Long someLongValue) {
+        this.someString = someString;
+        this.someInteger = someInteger;
+        this.someDouble = someDouble;
+        this.someBoolean = someBoolean;
+        this.someIntValue = someIntValue;
+        this.someDoubleValue = someDoubleValue;
+        this.someLongValue = someLongValue;
+    }
+
+    public Optional<String> getSomeString() {
+        return Optional.ofNullable( someString );
+    }
+
+    public Optional<Integer> getSomeInteger() {
+        return Optional.ofNullable( someInteger );
+    }
+
+    public Optional<Double> getSomeDouble() {
+        return Optional.ofNullable( someDouble );
+    }
+
+    public Optional<Boolean> getSomeBoolean() {
+        return Optional.ofNullable( someBoolean );
+    }
+
+    public OptionalDouble getSomeDoubleValue() {
+        return someDouble != null ? OptionalDouble.of( someDoubleValue ) : OptionalDouble.empty();
+    }
+
+    public OptionalInt getSomeIntValue() {
+        return someIntValue != null ? OptionalInt.of( someIntValue ) : OptionalInt.empty();
+    }
+
+    public OptionalLong getSomeLongValue() {
+        return someLongValue != null ? OptionalLong.of( someLongValue ) : OptionalLong.empty();
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/optional/nullvalue/Target.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.optional.nullvalue;
+
+import java.util.Optional;
+import java.util.OptionalDouble;
+import java.util.OptionalInt;
+import java.util.OptionalLong;
+
+@SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+public class Target {
+
+    private final Optional<String> someString;
+    private final Optional<Integer> someInteger;
+    private final Optional<Double> someDouble;
+    private final Optional<Boolean> someBoolean;
+    private final OptionalInt someIntValue;
+    private final OptionalDouble someDoubleValue;
+    private final OptionalLong someLongValue;
+
+    public Target(Optional<String> someString, Optional<Integer> someInteger, Optional<Double> someDouble,
+                  Optional<Boolean> someBoolean, OptionalInt someIntValue, OptionalDouble someDoubleValue,
+                  OptionalLong someLongValue) {
+        this.someString = someString;
+        this.someInteger = someInteger;
+        this.someDouble = someDouble;
+        this.someBoolean = someBoolean;
+        this.someIntValue = someIntValue;
+        this.someDoubleValue = someDoubleValue;
+        this.someLongValue = someLongValue;
+    }
+
+    public Optional<String> getSomeString() {
+        return someString;
+    }
+
+    public Optional<Integer> getSomeInteger() {
+        return someInteger;
+    }
+
+    public Optional<Double> getSomeDouble() {
+        return someDouble;
+    }
+
+    public Optional<Boolean> getSomeBoolean() {
+        return someBoolean;
+    }
+
+    public OptionalLong getSomeLongValue() {
+        return someLongValue;
+    }
+
+    public OptionalDouble getSomeDoubleValue() {
+        return someDoubleValue;
+    }
+
+    public OptionalInt getSomeIntValue() {
+        return someIntValue;
+    }
+}